Research On Cryogenic Performance Of SCQ And SSM Superconducting Magnets System For BEPCⅡ

The large-scale superconducting magnets are presently widely used in modern high-energy particle accelerators and nuclear fusion experimental device, which generally operate at liquid helium temperature region. Cryogenic technology is developing with the requirement of operation for superconducting magnets. In order to realize the goal of two orders of magnitude higher luminosity in Beijing Electron-Positron Collider Upgrade(BEPCâ…¡), three type of SC devices are to be applied, including a pair of superconducting radio frequency cavities(SRF), a pair of superconducting quadrupole magnets(SCQ) and a superconducting solenoid magnet(SSM). The performance of SC device and their cooling systems has great effects on the operation of BEPCâ…¡, which should be fully studied at the design stage. The cryogenic performance of SCQ and SSM superconducting magnets are investigated both at steady operation state and at unsteady state in detail, including flow and heat transfer characteristics of cooling medium, and electromagnetic, mechanical characteristics of magnets. The results are helpful for the long-term stable operation of magnets in BEPCâ…¡.Above of all, the temperature distribution along the SCQ magnets has been numerically simulated by computational flow dynamic software FLUENT. The heat loads from radial and axial supports were simulated considering variable physical properties of materials. The results are in good agreement with those by BNL. The temperature distribution of heat shields was simulated and the eight tubes cooling scheme was presented to replace the four tubes cooling scheme. The fluid flow along the cooling passage of SCQ magnets were compared for both supercritical helium cooling and subcooled liquid cooling. Based on the analyses, the supercritical helium cooling scheme was suggested.The heat loads from supports for SSM magnet were numerically simulated by finite element software ANSYS and the temperature distributions on the magnet and the LN2 heat shields were studied by FLUENT. The layout of cooling pipe was determined according to the above results. The magnetic force produced by SSM magnet on the anti-solenoid of SCQ magnet was calculated, which is in good agreement with that by BNL and IHEP. The magnetic flux was...